And while they wait, some companies, like Evernote, have gotten back on their feet. Last year Evernote was a poster child for the collapse of Silicon Valley, but after cutting back on staff and eliminating some employee perks, it has stabilized. “It was hard for employees to readjust expectations,” Mr. O’Neill said. “They had only known a world where another fund-raise was just around the corner.”

The biggest start-ups still attract investors, venture capital funds are still raising money and engineers can still command a high salary. That’s not to say some companies haven’t fallen by the wayside, but many of those who heeded the warnings have managed to stick it out.

It seems, if nothing else, that the doomsayers have at least pushed start-ups to shift from boasting about how fast they are growing to talking about financial responsibility.

The 124-Year-Old Start-Up

General Electric has been making a return to its heavy-industry roots while also trying its hand at becoming a start-up of sorts. In 2011 it opened a software center in San Ramon, Calif., with the aim to build an industrial operating system — a Windows or Android for factories.

Jeffrey R. Immelt, the chief executive, wants to be a “top 10 software company” by 2020. And he seems to have no Plan B.

The response? “They’re not software people,” was one of the skeptical comments.

G.E. has access to data from sensors in its machines that it uses to make software that helps predict whether a machine needs repairs. But by entering the software business, G.E. is also opening itself up to competition from a greater variety of companies.

And the stakes are high. For a consumer, a misfiring algorithm might mean a bad suggestion for what book to buy or what film to see. But if an algorithm prompts an airline to take a jet engine off the wing, it’s a $100,000 mistake.

The Case for an Interest Rate Increase

The Federal Reserve looks like it will probably raise rates in the coming months. “In light of the continued solid performance of the labor market and our outlook for economic activity and inflation, I believe the case for an increase in the federal funds rate has strengthened in recent months,” said Janet L. Yellen, the Fed’s chairwoman, said after last week’s annual policy conference at Jackson Hole.

Although the Fed is likely to consider a move at the next meeting, in September, many expect action to come in December, after the presidential election.

Some officials remain nervous about fragile growth, and there are questions about how the Fed could combat downturns in the future. If interest rates are not raised as much as during other periods of growth, they cannot be cut as much during downturns. Officials also remain skeptical about using negative rates.

“Central banks still have arrows in their quiver [although] they may not be as effective as they were before the crisis,” Randall Kroszner, a former Fed governor, told The Financial Times. But, he pointed out, “central banks can’t simply create growth.”

Still, perhaps they will take the advice they received from Christopher A. Sims, a Nobel laureate in economic science. What is that? Stop. You’re making things worse.

Mr. Sims argues that central banks need to say publicly that more government spending is required to stimulate economies. “So long as the legislature thinks it has no role in this problem, nothing is going to get done,” he said.”

Coming Up

The Commerce Department reports data on spending in July, which is expected to have dipped slightly.